1. Field of the Invention
The present invention relates to thermoplastic rail systems, and more particularly to an expansion joint for use with such thermoplastic rail systems.
2. Description of the Prior Art
Railings serve the purpose of guard rails, hand rails, grab rails and in many instances serve as area dividers. Railings have long been used for a variety of applications, such as multi-story buildings with stairways, balconies, patios, industrial buildings, playgrounds and schools, among any number of other wide variety of uses. These uses are both indoors and outdoors. Outdoor railing systems are exposed to the weather and other corrosive elements such as salt water, chemical vapors and the like. In addition, outdoor railings are subjected to temperature differentials and in some instances depending upon the location, extreme temperature differentials.
Building codes require the use of high strength material such as iron, steel, aluminum and the like to provide the sufficient rigidity and strength to insure adequate safety and security qualities depending upon the location and purpose of the railing system. Thermoplastic railing systems have become popular due to certain intrinsic qualities of the thermoplastic as set forth hereinafter. In order to meet building codes, thermoplastic railing systems typically include a plurality of vertical posts which are mounted or secured to a base or decking member. These vertical posts typically have a tubular steel reinforcing member which is positioned within a tubular thermoplastic pipe formed from materials such as acrylonitrile styrene acrylate (ASA), PVC, acrylic or the like, in order to meet the necessary rigidity and strength requirements.
These vertical posts interconnect with one or more horizontal rails which in turn may have vertical balusters extending therebetween. Usually at least one of the horizontal rails and in most instances, the top most rail of the railing system also includes a tubular steel insert within the thermoplastic tubular member, this tubular steel insert being aligned and secured to vertical posts having a tubular steel reinforcing member. The tubular steel insert in the rail may or may not run continuously throughout. The intermediate vertical balusters and horizontal rails which do not have structural metal inserts are commonly referred to in the trade as in-fill area posts and rails.
While thermoplastic rail systems solve many of the problems experienced by metal railings due to weather and corrosive elements, one of the problems with thermoplastic rail systems which has not been adequately solved is the manner in which it accommodates thermal expansion and contraction of the horizontal rails or balusters. Thermal expansion and contraction solutions in the past, while meeting the strength and rigidity requirements, have failed in the aesthetic requirements in that thermal contraction resulted in a visible gap between the mating members of the horizontal rails and vertical posts or horizontal rails and balusters.
The present invention provides for an expansion joint which meets or exceeds the strength and rigidity requirements and solves the aesthetic problems experienced by thermal expansion and contraction.